There is a type of LED illumination in which light from an LED is guided into a light guiding body and at the same time, the light is diffused and emitted to the outside by a diffuser included in the light guiding body.
For example, a system that uses an LED as a light source and guides light from the light source to a light guiding body using a reflector is known. Based on such a structure, direct light from the LED can be blocked. Thus, glare of direct light can be reduced. However, the reflector made of metal absorbs about 10% of light in one reflection, leading to a lower light output ratio. On the other hand, if the light guiding body is made thicker, the plane of incidence of the light guiding body is increased and the light output ratio can be improved. However, if the light guiding body is made thicker, the weight thereof increases correspondingly and also material costs increase and therefore, a thinner light guiding body is desired.